The primary Genetic Resource at The Jackson Laboratory (TJL) is mice. Over 2400 strains maintained in the various components of the Genetic Resource provide a more extensive and diverse array of genetically defined mice than any other mouse breeding resource in the world. The Mouse Models Resource maintains and provides to Cancer Center members specialty strains and stocks that are useful for basic biomedical research into mechanisms of cell cycle control, immune recognition and response, and development, as well as mouse models of human inherited disorders. The various types of strains in this Resource are organizationally consolidated under the direction of Dr. Muriel T. Davisson, the Director of Genetic Resources. The Mouse Models Resource contains mouse strains carrying spontaneous, induced, and genetically engineered mutations; mice with chromosome aberrations, and special inbred strains, including wild-derived inbred, Recombinant Inbred (RI), and congenic strains. The colonies are insured by cryopreservation of embryos and gametes through the Cryopreservation Resource, and DNA from most strains is available through the Mouse DNA Resource. Mouse Models Resource personnel provide genetic expertise and advice, colony maintenance advice, including special husbandry needs, and biological information about the mice in the Resource. The Mouse Models program also maintains databases of scientific and biological information on strains held at TJL.